Balancing Varroa management and honey bee resilience: Behavioral and physiological consequences of temporarily high mite pressure

Abstract

Pollinators are essential for global agriculture and ecosystem stability, yet many populations are declining due to parasites and pathogens. Among these, the ectoparasitic mite Varroa destructor is one of the most critical challenges to honey bees (Apis mellifera). Conventional treatment approaches use frequent interventions to keep mite levels as low as possible, whereas other approaches aim to promote natural selection by omitting treatments. A possible compromise lies in reducing treatments while maintaining colony survival through targeted interventions. This approach may allow adaptive responses under temporary mite pressure. In this study, we compared two beekeeping strategies: 1) Conventional beekeeping practice involving regular drone brood removal during mating season, formic acid treatment in summer, and oxalic acid treatment in winter. 2) An innovative approach where drone brood is left in the colony and a summer brood interruption is induced, followed by an oxalic acid treatment. Winter treatment is only applied if Varroa pressure exceeds three naturally dropped mites per day shortly before winter treatment. We investigated Varroa infestation and its consequences for honey bee foraging behavior, homing ability, juvenile hormone III levels, pollen protein content, and honey yield. Bees from innovatively managed colonies started foraging earlier and had elevated juvenile hormone levels at young ages. Orientation ability was unaffected, but these bees performed longer foraging trips and collected pollen with higher protein content. They also stopped foraging earlier, likely reflecting a reduced lifespan due to increased Varroa pressure. Nevertheless, colony productivity did not differ between the two beekeeping approaches. Our findings suggest that reduced Varroa treatments and temporarily high mite pressure do not have negative effects on colony performance. Such approaches may offer a potential middle ground between intensive conventional management and selection-based strategies, balancing colony vitality and the possibility of fostering resistance traits through controlled exposure of parasite and host.